Sweetening of petroleum fractions, such as naphtha boiling range hydrocarbons or other liquid hydrocarbons, that contain mercaptans (or sour petroleum fractions) are well-developed commercial processes commonly used in many petroleum refineries. In the sweetening process, mercaptans contained in the feed hydrocarbon stream (e.g., sour hydrocarbon stream) are converted to disulfide compounds that remain in the hydrocarbon stream (e.g., sweetened hydrocarbon stream). Sweetening processes, therefore, do not remove sulfur from the hydrocarbon stream but rather convert the sulfur to an acceptable form. The sweetening process involves an admixture of an oxygen-containing stream to the sour hydrocarbon stream to supply the required oxygen. The admixture of hydrocarbons and oxygen contacts an oxidation catalyst in an aqueous alkaline environment to oxidize the mercaptans.
Typically, a caustic (e.g. an aqueous caustic solution) is combined with the sour hydrocarbon stream to create the aqueous alkaline environment. After contacting the oxidation catalysts, at least a portion of the caustic is carried with the sweetened hydrocarbon stream and can be problematic for further downstream processing. Current approaches for removing caustic from sweetened hydrocarbon streams often require additional downstream equipment items and can be costly and/or are relatively inefficient.
Accordingly, it is desirable to provide apparatuses and methods for the oxidation of mercaptans contained in a feed stream that includes liquid hydrocarbons such as naphtha boiling range hydrocarbons or the like for forming a sweetened hydrocarbon stream with enhanced removal of caustic from the sweetened hydrocarbon stream. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background.